Multiprotocol Label Switching
Multiprotocol Label Switching (MPLS) has gained popularity as a method for efficient transportation of data packets over connectionless networks, such as Internet Protocol (IP) networks. MPLS is described in detail by Rosen et al., in Request for Comments (RFC) 3031 of the Internet Engineering Task Force (IETF), entitled “Multiprotocol Label Switching Architecture” (January, 2001), which is incorporated herein by reference. This RFC, as well as other IETF RFCs cited herein below, is available at www.ietf.org/rfc.
In MPLS, each packet is assigned to a Forwarding Equivalence Class (FEC) when it enters the network, depending on its destination address. The packet receives a fixed-length label, referred to as an “MPLS label” identifying the FEC to which it belongs. All packets in a given FEC are passed through the network over the same path by label-switching routers (LSRs). The flow of packets along a label-switched path (LSP) under MPLS is completely specified by the label applied at the ingress node of the path. Therefore, an LSP can be viewed as a tunnel through the network.
MPLS defines a label distribution protocol (LDP) by which one LSR informs another of the meaning of labels used to forward traffic between and through them. Another example is RSVP-TE, which is described by Awduche et al., in IETF RFC 3209 entitled “RSVP-TE: Extensions to RSVP for LSP Tunnels” (December, 2001), which is incorporated herein by reference. RSVP-TE extends the well-known Resource Reservation Protocol (RSVP), allowing the establishment of explicitly-routed LSPs using RSVP as a signaling protocol. RSVP itself is described by Braden et al., in IETF RFC 2205, entitled “Resource ReSerVation Protocol (RSVP)—Version 1 Functional Specification” (September, 1997), which is incorporated herein by reference.
Section 1 of RFC 2205 defines an “admission control” decision module, which is used during reservation setup to determine whether a node has sufficient available resources to supply the requested quality of service. The admission control module is used in RSVP-TE for setting up MPLS tunnels.
U.S. Patent Application Publication US 2002/0110087 A1, entitled “Efficient Setup of Label-Switched Connections,” whose disclosure is incorporated herein by reference, describes methods and systems for carrying layer 2 services, such as Ethernet frames, through label-switched network tunnels.
Ethernet Link Aggregation
Link aggregation (LAG) is a technique by which a group of parallel physical links between two endpoints in a data network can be joined together into a single logical link (referred to as a “LAG group”). Traffic transmitted between the endpoints is distributed among the physical links in a manner that is transparent to the clients that send and receive the traffic. For Ethernet networks, link aggregation is defined by Clause 43 of IEEE Standard 802.3ad, Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications (2002 Edition), which is incorporated herein by reference. Clause 43 defines a link aggregation protocol sub-layer, which interfaces between the standard Media Access Control (MAC) layer functions of the physical links in a link aggregation group and the MAC clients that transmit and receive traffic over the aggregated links.
U.S. Patent Application Publication US 2004/0228278 A1, entitled “Bandwidth Allocation for link Aggregation,” the disclosure of which is incorporated herein by reference, describes methods for bandwidth allocation in a link aggregation system. The methods described in this publication are meant to ensure that sufficient bandwidth will be available on the links in the group in order to meet service guarantees, notwithstanding load fluctuations and link failures.